


23% more efficient

by checkmate



Category: Marvel Cinematic Universe, The Avengers (Marvel Movies)
Genre: Arc Reactor Kink, Boys Kissing, Comeplay, M/M, Post-Avengers (2012), Riding, how did this end up so long, it is slow build gay then fast build GAY SEX, pre everything else, questionable science, some light pain play
Language: English
Status: Completed
Published: 2015-10-03
Updated: 2015-10-06
Packaged: 2018-04-24 15:46:03
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 2
Words: 11,774
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4925557
Author URL: https://archiveofourown.org/users/checkmate/pseuds/checkmate
Summary: <blockquote class="userstuff">
              <p>Tony begins to suspect that Bruce has an arc reactor kink, so naturally finds as many excuses as possible for them to spend time in the lab together. Shirtless. For science.</p>
            </blockquote>





	1. The Build Up

**Author's Note:**

> Based on [this beautiful piece of artwork](http://rainbowroute.tumblr.com/post/79341648509/bruce-finds-comfort-in-that-small-light-in-tonys#notes). It was meant to be a one shot but it is now a two shot because it exceeded 10k and that felt too long for a one shot with essentially no plot. So expect the next part within the next few days because it is finished.
> 
> This is set immediately after the first Avengers movie (like a week after) which was fun to write and doesn't get touched on enough, I think. OH and yeah sorry all the sex is in chapter two.

Tony doesn’t hear the door open, but he does hear Banner’s stammered apology. “Shit. Sorry Tony, I should have knocked. Or something. Alerted JARVIS, maybe? I don’t really know what the protocol is.”

Tony puts down the arc reactor, and turns to see Bruce looking panicked and bumbling and ridiculous. It’s adorable. “No worries, Banner.” He says airily, but he’s interested in seeing his fellow scientist’s reaction to the giant metal lined hole in his chest. Even Natasha squicked out a little when she had first seen it.

“Do you want me to leave?” He asks nervously, managing to almost entirely keep eye contact with him. His gaze only flicks down briefly. “Pepper said—” He starts, before he ends the sentence abruptly.

Tony sighs. He knows what Pepper said—don’t bother him when he’s tinkering with the arc reactor. She plays it off like it’s a highly dangerous enterprise that could blow up at the slightest wrong touch or whatever, but Bruce is too smart to buy that. The damn thing lives in his chest, for God’s sake. It’s clearly not that sensitive.

Tony doesn’t like being bothered when he’s tinkering with the arc reactor because he fucking hates feeling vulnerable like this. He’s pretty sure Bruce knows this too. When he doesn’t answer immediately, Banner starts backtracking and goes to let himself out, but Tony stops him. “Is it urgent?” He asks, and Bruce hesitates. “Whatever you came up here for. Can it wait?”

“What? Oh. Uh, yeah I guess. Barton ordered takeout and I thought I should let you know before Steve and Thor inhale all the pepperoni.”

Tony considers it for a second. “How hungry are you?”

Bruce cocks his head to the side slightly, a cute habit that Tony has noticed when he’s trying to figure out the implications of something. “I could wait.” He counters eventually, and Tony beams.

“Want to help me with something?”

“If it involves sticking my hand in your chest, I’ll warn you, I have really chubby uncoordinated fingers.” He says immediately, and Tony can’t help but tut.

“Does Pepper tell _everyone_ that story?”

Bruce smiles, and re-closes the door. “Only when she’s drunk.” He walks up to Tony’s work bench, the fucking mess that it is, and perches his ass on the corner. “I can’t promise anything, but I’ll have a go.”

It’s been barely a week since aliens literally tried to take over the world, and barely a week since everyone decided it would be a great idea to move into the remains of Stark Tower, despite the fact that the top five floors had to be demolished and are being rebuilt from scratch. No-one wants to be alone, at least for a while, and even with five floors missing, Tony has the most space. Natasha can apparently settle anywhere, and Clint’s spent most of his time sleeping, still in recovery. Steve is still getting used to the twenty first century and it doesn’t really matter where he does it, since a cardboard box under a bridge is better than both World War Two and 1940’s Brooklyn. Thor’s from a whole different realm. Thor can adjust to anything.

But Bruce—Bruce is still getting used to being around people, to living in the developed world, but most of all, living with _him._ After all they’ve been through, the poor guy _still_ gets star-struck. For anyone else, Tony would understand, but he’s pretty sure he’s the one who should be getting star-struck. Bruce has the most astonishing scientific mind he has ever encountered, and he feels inadequate being in the same room as him sometimes. He’s been trying to get Bruce up into his R&D candy land since the helicarrier.

“I’m sure your vast and varied scientific knowledge will suffice.” He says, rolling his eyes. Bruce still makes an effort not to look at the metal cylinder going through his chest. Tony appreciates it, but it’s not really necessary. “It doesn’t bite, you know.” He gestured at the hole, and Bruce blushes. “Got any thoughts on making the vibranium core last longer? This shit ain’t in infinite supply and I’m getting through it much faster than I’d like.”

“You know I’m not an expert on arc reactor technology.” He protests weakly, looking down at the blue glowing light on the work bench nervously. “Why don’t you ask Steve? I’m sure he knows more about this than me.”

Tony looks at him for a split second, before they both start laughing. “Okay, Steve probably knows nothing about it.” Bruce acknowledges. Tony can’t really remember seeing him laugh before; it’s a nice sound. Relaxing.

“Dad didn’t have much time for giving anyone a science lesson.” Tony agrees. He’s pretty sure he’s gleaned everything the old records—both SHIELD and his personal stash—will reveal, but it’s not enough. He’s still burning through a vibranium core every fortnight or so, and the more he needs, the more he is indebted to SHIELD. He hates owing people things.

“Have you spoken to Carter?” Bruce asks, sounding like he’d really rather not be asking. “I hear she’s, uh…”

“Still alive?” Tony provides helpfully. “I spoke to her a while ago. Howard _really_ wasn’t big on sharing. Either she didn’t know anything, or she’s an exceedingly good liar.”

Bruce hums under his breath. “I guess I could take a look.” He says eventually, and Tony grins. He has suspected a scientific challenge might be enough to crack Banner out of his funk—he hopes he’s right. “But I’m not promising anything.”

“No promises required.” Tony wheels his chair back to allow Bruce a closer examination, smiling smugly. The scientist’s eyes widen when he begins examining the metal work, turning it over in his hands with the kind of reverence Tony only holds for whiskey and really good cheeseburgers. “Like what you see?” He grins obnoxiously. Bruce doesn’t even roll his eyes, too enraptured with the design.

“I… Y-Yeah. Tony, this is incredible. It’s genius.”

“You’re saying this like you’ve only just realised.” He already knows it’s incredible and he’s been told many times before, but something about Bruce Banner’s seal of approval is immensely satisfying.

“You built one of these in a cave?” He asks, sounding slightly sceptical.

“Well. Kinda. It was a bit shit, to be honest. And it was killing me. But essentially, yes.”

“How long can you leave it out?”

Tony pulls a face. “Uh. Probably should have put it back in ten minutes ago.” Bruce shoves it at him wordlessly, panic etched on his face. “I’m not going to die, Bruce.” He reassures him with a roll of his eyes. “Give me a hand.”

He’s rigged up a system that’s slightly more elaborate than Pepper sticking her hand in the hole, but it’s still much easier with another person to help. As Tony pulls the wire clear from the casing, Bruce takes it and connects it into the back of the arc reactor with great care. “It’s beautiful.” He murmurs, touching it lightly when it is securely back in Tony’s chest. His finger traces the ring where metal meets sensitive flesh, the wonder obvious on his face, before he realises what he’s doing. “Shit. Sorry. _Sorry._ I… Sorry.” He apologises profusely, but Tony just smirks.

“I know. Sometimes stroking my chest can be hard to resist.”

Bruce blushes some more, the red tinting his cheeks unbelievably adorable. He can barely tear his eyes away from Tony’s torso. He’s flattered. “Sorry.” Bruce says again, and makes towards the door.

“Don’t be.” Tony says with an unashamed grin, and grabs his shirt from the back of his chair. When his head pops out the top, Bruce still stands awkwardly in the door. “You want to grab some food?”

“There’s pizza in the kitchen.” Bruce replies dumbly.

“Pfft. I highly doubt there is any pizza left in the kitchen. Come on, Banner. My treat. I want to pick that big sexy brain of yours.”

Bruce scuffs a socked foot on the floor, before relenting. “Fine. Okay. Good. Yeah. … Food.”

Shit, he’s so awkward.

Tony smirks.

*

“But that’s what I’m saying! Get rid of all this and you’ll cut your power consumption by at least ten percent. Thirteen percent at a push.”

“But the _aesthetic,_ Bruce.” He says firmly, but he’s joking. He knows Bruce is right, but he enjoys winding him up all the same, seeing how far he can push before he withdraws back into his shell. Bruce’s eyes shine when he gets excited, his wild curls falling down in front of his face. Tony catches himself noticing the soft curve of his lips as he frowns in annoyance.

“You asked for help making your heart battery more efficient and you’re concerning yourself with the aesthetic. Seriously, Stark?” The eye roll just tops it off as Bruce stands up, pushing his lab stool back with a deep huff. This is hilarious. He tries to conceal his amusement, but Bruce sees his smirk and scowls. His brow furrows and his nose wrinkles a little, and it’s so cute.

“What can I say?” Tony purrs. “I’m very appreciative of aesthetic.”

“Well, maybe you should be more appreciative of scientific breakthroughs.” He snaps, and oh shit, okay, apparently Bruce doesn’t realise that he’s totally been flirting for at least three hours. Crap.

“Bruce, come on—” He starts, trying to stop Bruce storming out in frustration.

Bruce spins on his heel and jabs a finger into his chest. Tony hisses as it lands on the sensitive skin joining the arc reactor casing; it does hurt, but he _might_ have exaggerated just a little to play into Bruce’s tendency to fret over him. It works. He only feels slightly bad when Bruce switches immediately to his guilt complex. “Fuck! Tony, god, I’m sorry, I didn’t think. I didn’t mean to hurt you.”

“Kiss it better?” Tony tries, because apparently subtlety isn’t working.

Usually he’s back instantly with a sharp retort or sarcastic comment, but for once, Bruce hesitates before giving him a tight smile. “Hilarious, Stark.” He says, and turns to leave.

“Wasn’t joking, Banner.”

Bruce freezes. Tony can’t see his face, but he can imagine the lines of reasoning Bruce’s brain must be processing right now. He turns slowly, a blush spreading across his cheeks. Tony’s not even sure he plays for the right team. Probably should have thought of that, but spending too much time with his fellow Avengers is starting to make him forget that straight people actually exist. They’ve been through enough together that shared experience trumps such concerns.

“Pepper—”

“Was more than just friends with Agent Coulson, let me tell you. You know Happy? They date frequently. Besides, she likes you.”

Bruce mulls that over, and Tony gives him some time to process it. Not everyone is down with relationships as open as theirs. Eventually, he asks, “She likes me?”

Tony lets out a snort of laughter. “That’s what you take out from that? In fact, she specifically told me that I should jump you before she gets there first. But I’m not that crude.”

Bruce looks bewildered at the turn of events, but Tony can handle bewildered. “If you’re not interested, no hard feelings, Banner. I’m not going to be _too_ hurt.” As he says it, he considers their newly formed, tentative friendship, and wonders whether he could handle the tease of Bruce’s unintentional hotness on a regular basis. Possibly not.

“Does that seriously usually work? You’re not used to getting rejected, are you?” Bruce says with a slight shake of his head. Tony definitely feels disappointed, almost hollow. “Goodbye, Tony.”

“Did I come on too strong?” He shouts after. “Fuck.”

Bruce has barely stepped out of the door when Pepper lets herself in. “Was that Bruce I just passed in the corridor?” She says knowingly. “Totally knew you were lying about not boning him.”

Tony scowls. “Did you really just use the word boning?” He tuts in disbelief. Totally avoiding the actual question.

“He rejected you, huh?” Pepper says, and Tony swears she can read his fucking mind. “Never mind. Maybe he’s straight.”

Tony groans. “I should probably check these things before I humiliate myself.”

“Remember that for next time?” She advises, before drawing a stack of papers from a folder tucked under her arm. “Can you sign these for the contractors before you retreat into your den of self-pity? We have to get these in by tomorrow or we won’t get the new windows in time to have them fitted before the—”

Tony grabs the papers from her hand and scribbles his name on the line she has marked with a Post-it. “In what world do you think I care?” He grumbles, thrusting them back into her arms. “Is that everything?”

“I need you to sign this card, too.” She says. He flicks it open to see the rest of the team’s autographs on it already, including Bruce’s.

“What’s the cause?” He asks, because it’s bound to be for a charity auction. Their collective celebrity has made a group autograph a top money spinner at fundraisers. Steve encourages them to do as many as possible, but doesn’t seem to realise that the more things they sign, the less they are worth.

“Clearing up your mess downtown.” She says, and he grimaces. They might have saved the world from aliens, but there were plenty of people who lost lives, homes or jobs before he could get a nuke in that fucking wormhole. The clean-up has cost millions already, and they were still pulling a few bodies from the rubble.

“Donate ten million and tell whoever’s organising it that I’ll do one of those A Night With Tony Stark disasters for the auction.” He says, knowing he’ll probably regret it when it actually happens. Pepper looks surprised; he doesn’t do mixing with people, _ever_ , but this Manhattan thing is a massive fuck-up and if he has to lose a night of his life to raise a bit more money, he’ll happily do it. Billionaire, philanthropist—he isn’t letting Rogers think that was all just talk.

“How generous of you.” Pepper says, and she’s not entirely joking. “It’s next week and yes, you are expected to attend. On time if possible.”

“Yeah, whatever, I’ll be there.”

Even Pepper, who is an expert at disguising her surprise, looks slightly taken aback, but she doesn’t question it. “Right. Excellent.” She says briskly, taking the card back. “And you should really go to bed, Tony. You look tired.”

He nods absently, making a vague promise to come down soon. He doesn’t. He doesn’t have the heart to tell her that he can’t sleep for the nightmares.

*

“Did you try stripping off the external casings?” Bruce asks as he enters the lab bright and early the next morning. Tony jumps, not expecting company, but he doesn’t apologise for letting himself in today. Clearly Bruce is adjusting to his environment well.

“Oh. Uh. Yeah.” Tony says, holding the new reactor out to him. Bruce takes it, and sits down next to him anyway to inspect it. “I can’t take too much out, else it’ll be too small for its socket.” He explains. “And  I don’t much fancy replacing this-” He taps his chest lightly. “Any time soon.”

Bruce smiles tightly, his eyes lingering on Tony’s bare chest for just a touch too long. “Understandable. What are your savings with this one?”

“7%, according to JARVIS. I mean, it’s a start.”

“It glows too much.” Bruce says firmly. “Every joule of energy you’re wasting with that stupid blue light is a joule not being used to power your damn heart.” Tony opens his mouth to protest, but Bruce cuts him off. “If you say _anything_ about an aesthetic, I swear I will go back to India, take the reactor with me and leave you here to slowly die.”

Tony winces, but swallows his comment about the reactor being essential at glow parties.

“Sorry, that was—”

“Kind of dark.” He finishes, half way between impressed and trying to stop his hands shaking. “I like it.” He lies.

“Really, really inappropriate.” Bruce says seriously, and hands the reactor back to Tony gently. “And not something to joke about. I’m really sorry.”

“Don’t sweat it.” He breezes, trying not to sound false. From anyone else, he would probably be freaking out right now, but he knows Bruce won’t hurt him, even if the guy does have some major issues. “No harm done. You’re right about the light, though, loathe as I am to admit it.”

Bruce sends him a small smile, and begins suggesting ways to reduce the power wastage. It’s relaxing work, bouncing ideas off of each other and actually being able to talk science for once. Three hours pass, and when they plug the reactor back in, it lights up a clean, soft white. “What are the readings, J?” Tony asks as he tries to accustom himself with the new colour scheme.

“14% improvement over the original model.”

Bruce hums, taps the glass frontage lightly. “It’s getting there.”

“Got any more plans to ruin it in the name of improvement?” Tony teases, not really expecting an answer.

“It’s warm.” He says, thinking out loud. “Doesn’t that feel weird?” Tony shrugs. He’s pretty much got used to it now, but initially it had been the hardest thing to adjust to. “It’s wasting energy through here, too. If we can increase the efficiency for heat as well as light, we could shave another two or three percent off.”

“You’re really getting into this, aren’t you?” Bruce blushes, looking down at his hands. “No, it’s good. I’ve never seen anyone as enthusiastic about the arc reactor that wasn’t trying to steal it to fuel a global arms race.”

Bruce lets out a reluctant laugh. “I like working on new projects.” He admits. “And I… I like working with you.”

“I’m sure we can find something new to work on once this has been pushed to the limit.” He offers. Bruce’s vast intellect would be a valuable addition to his team. By now, he’s searching for reasons to keep him around.

Banner mumbles something under his breath about not wanting to intrude. “Don’t be stupid, Banner. Besides, I’m sure you can get the reactor even more efficient if you tried.”

Bruce purses his lips as he studies the metal. Tony’s had it out too much today already, so he’s having to do his inspection while it’s fixed in his sternum, which is highly amusing. Tony exaggerates his shivers when Bruce brushes against sensitive flesh, and Bruce tries to act all platonic and innocent as he touches up Tony’s bare chest. It’s great fun.

“Have you tried different metal alloys for the components?” He says eventually, removing his glasses. He wipes at them with the hem of his shirt, which can only have caused them to smudge more. “If you used a metal that conducted less heat, you’d get more output.”

“But by definition, it has to be a good conductor.”

Bruce shrugs. “Of electricity. Not heat. You’re the expert, but it could be worth looking in to.”

Tony mulls it over, immediately considering the relevant properties of tens of different materials. He couldn’t be sure, but Bruce might have a point. If it were anyone else, Tony would be jealous and beyond infuriated at his seemingly endless array of useful ideas, but he couldn’t be angry at Bruce. The guy is so damn likeable, the Hulk aside, and he’s remarkably humble for the extent of his genius.

“Think it over, anyway.” He says shortly, and stands to leave. Tony reaches out instinctively and grabs his wrist.

“You want to get dinner?” He asks, before letting Bruce go because he realises he’s being weird. “I’m really hungry. Let’s get dinner.”

“It’s two in the morning.” Bruce says delicately, looking down at him with a slight amused smile. “But I can cook, if you want.”

“What? Oh.” He hadn’t realised the time, and he wasn’t really that hungry. He’s pretty sure Bruce knows as much from the smug look on his face. “No, it’s fine.”

“I make a mean ramen.” He offers, enjoying Tony feeling uncomfortable. “No? Okay.”

The only way for Tony to win is to beat him at his own game. “Actually, yeah. Why not? Ramen.”

Bruce doesn’t falter, and heads towards the door. “It’s vegetarian ramen, I’m afraid.” He says conversationally. “But I’ve been told by many people that it’s very good.”

Tony rolls his eyes, and strongly suspects he’s going to get something out of a packet that includes some dodgy flavour powder as Bruce’s idea of a joke. He plays along anyway, though. “You cook for people a lot?” He asks, and gets a meagre shrug in response. “Then I’m hurt that you’ve never cooked for me.”

Bruce glances at him to see if he’s joking, but Tony won’t give anything away. He enjoys the tentative repartee he shares with Banner, even if it is mostly petty point scoring. He has achieved his original goal of making the other man hang out with him a little longer, but now it’s on Bruce’s terms, and that puts him on edge. Still, he isn’t one to back down from a challenge.

“I guess I thought the great Tony Stark would be above the kind of food that I make. That is, essentially vegetables and noodles and water.”

Suspicions confirmed, Tony laughs. Bruce’s floor is less well furnished than the ones higher up, but he’d never requested more furniture. “You know you can order whatever you need for this place.” He says. He’s not had a reason to come in since Bruce moved, but it’s still pretty much empty. There’s a shitty old couch with stained cushions that he refuses to believe was actually in Stark Tower when Banner arrived, and a rattling table, and that’s pretty much it.

“I have everything I need.” Bruce shrugs.

Tony grins knowingly. “You still think you’re going to get out of here sometime soon, don’t you? Go back to Kolkata or Moscow or Shanghai and help diseased orphans.”

“And what? You’re going to stop me?” Bruce laughs at the mere thought, and Tony is very aware that if he really wanted to leave, it would be foolish to attempt to prevent it.

“In a way.” He says cockily anyway. “Give it another week and you’re not going to want to go anywhere.”

“You’re infuriating.” Bruce says flatly, and sets a kettle full of water to boil. It’s only when he actually starts pulling mushrooms and peppers and green onions from the little fridge that Tony realises Bruce fully intends to cook for him. From scratch. Not out of a packet. “Make yourself at home.” He says when he notices Tony still hovering awkwardly in the entrance to the kitchen. “There’s only one chair, but I guess you can sit on the couch.”

“Can I help?”

Bruce takes one look at him and actually snorts with laughter. “Tony, sit down before you embarrass yourself. Have you ever cooked anything in your life?”

He thinks back to a charred, bitter mess in an airplane kitchen a few months ago and realises Bruce has a point. And like Bruce said, ramen is vegetables and noodles and water. His assistance isn’t necessary. As he sits on the saggy couch though, he feels like Bruce is winning their battle of sarcastic banter.

Barely five minutes later, a large bowl of steaming vegetables and noodles and broth is pressed into his hands. It smells fucking amazing, and it tastes even better. “Where did you learn to cook like this?” He manages between deep gulps of scalding hot, sweet and salty soup.

Bruce smiles, proud of himself. “This? In Japan.”

“I swear you’ve travelled even more than me.”

“That’s the thing about being on the run, I guess. Seen a lot of the world. Traded a lot of medical help for food. You should try my vegetable curry sometime. Straight from the bits of Mumbai that were really not designed for tourists.”

“You miss it.” Tony states. It’s clear in his tone, in his eyes, in the way he clutches at a bowl of fucking ramen like a lifeline.

“I miss bits of it. I miss helping people.” He agrees. “I don’t miss getting hunted. I don’t miss sleeping on street corners or in slums and wondering if I was actually going to wake up. I don’t miss the Other Guy constantly under my skin, itching to come out.”

Tony wonders whether he should ask his questions about the Other Guy, as Bruce refers to him, or whether it’s inappropriate. But he’s left an opening for it, and God knows when he might get the courage to ask again. “So you don’t feel him anymore?”

Bruce chuckles, and reaches for the glass of tap water he poured himself. “I always feel him. But he hadn’t been out in over a year before last week. It’s like he’s a really, really violent and destructive puppy, and the Battle for Manhattan was the best walk in the park _ever_.”

“With giant robot whales and an evil psychopathic demi-god.” Tony adds, trying to make Bruce smile and lose the tension building up in his body. “It’s gonna take something pretty special to top that, big guy.” It works; Bruce laughs and relaxes into the couch, neatly swirling a few strands of noodles around his fork. He manages to eat it without splashing little drops of soup everywhere, which is a skill Tony hasn’t quite acquired yet.

“I’m sure something new will turn up soon enough.” Bruce jokes.

Depressingly, he’s probably right.

Tony slurps up the last dregs of ramen broth, and finds himself surprisingly tired. He stifles a yawn, getting up to put his bowl in the sink. “Thanks for dinner, Bruce.” He is genuine in his gratitude; it’s been a long time since someone actually cooked for him. He can’t even remember when. He lives off of coffee and Pop-Tarts and take out. It’s fine most of the time, but the real deal is nice sometimes too.

“We should do this again sometime.” Bruce says. It could be innocent if it weren’t for the blush spreading across Bruce’s face. Interesting. Tony notes it away in his mental Bruce Banner file. Maybe the super obvious come on had been too much, but that doesn’t necessarily mean Bruce isn’t interested.

*

Tony hates these charity things normally. Pepper is ruthlessly efficient and a god send when it comes to whispering the names of important guests in his ear three seconds before they greet him enthusiastically. She deals with the small talk while he fields questions about donations and the Iron Man suits. But Pepper isn’t here tonight; she’s otherwise engaged across town, and Tony is alone.

Sure, the rest of the team is here, but Natasha and Clint tend to pair up for these kinds of things, and Tony has no intention of forcing Clint to face this without her support. The poor guy still struggles with his actions under Loki’s instruction, and some people find the mind control excuse a little _too_ convenient. Steve is a natural born charmer and Thor loves any excuse for a celebration, so they both involve themselves with pleasure.

He’s amazed this many people bothered to show up at all to be honest. The marketing for the relief appeals have categorised Asgardian alien invasions as a natural disaster, but Tony’s not sure he’d be as comfortable swallowing it. Really, it’s SHIELD’s mess to clean up, not the general public’s, and he’s still expecting someone to turn around and label them public enemies, numbers one through six.

“I hear you’re up for sale.” A voice says conversationally in his ear, and he turns to see Bruce in a beautifully cut suit looking incredibly uncomfortable.

“You going to bid for me, Banner?” He Bruce didn’t respond immediately, nor move out of Tony’s immediate personal space. He can practically hear his heart beating in his ribcage.

“We both know I can’t afford you.” He says, but there’s the smallest touch of regret in his voice.

Tony let his fingers brush along Bruce’s neck, cleanly shaven for the first time in over a week, before letting his hand drop. Bruce holds his breath for longer than necessary before letting the air out in one large gust. “I don’t know, Banner. You look a million dollars in that suit.”

Bruce laughs, and takes a step back, moving to a more respectable distance to be seen in public. “Is that the best you’ve got?” He looks Tony up and down with no subtlety, his gaze pausing on his chest. Tony supposes it can’t be helped; he is very aware of how great he looks right now.

“Whatever. I’m going to be auctioned off for more than a million dollars anyway. You really are rocking that suit, though.” And he is, the crisp lines and tight fabric emphasising a physique usually hidden behind baggy shirts and slacks that practically fall off at the hips, they’re so loose.

“You look good too. You always look good.”

“They say God made me just to wear a tux.” He claims in all seriousness, and does a slow spin so that Bruce can admire him from all angles. Bruce’s eyes linger on the pale glowing under the buttons of his shirt, and he swallows. If he looks good enough to make Bruce do a double take, Tony knows he is definitely going for more than a million dollars. “You know, I could always loan you the money.”

Bruce blinks in surprise, tearing his eyes away from the hidden reactor, before he links the words back to their earlier joke. “Huh?”

“You get an evening with Tony Stark, the charity gets their money and I don’t have to spend a night with a creepy stranger. It’s a win—win situation, Bruce.”

“Assuming I want an evening with Tony Stark.” A week or two ago, Tony might have considered Bruce’s words to be serious, but now he knows that it’s all just a part of their carefully choreographed dance. “You’re not escaping from this. Let people actually bid properly. We have all the other nights.”

Tony’s eyes widen at the promise. “We do? All the other nights, huh?”

Bruce blushes horribly but doesn’t take the words back. This night is revealing more and more to Tony as the minutes tick by. “We should mingle or whatever.” Bruce says hopelessly, and slips off into the crowd without another word. Tony knows he’s not mingling—Bruce didn’t much fancy this many strangers all in one place—and Tony guesses he’s probably hiding in a bathroom or something.

He’s expected to mingle though. His laugh sounds more and more forced as the evening gets later but he perseveres for the sake of charity. If his stories can guilt trip a few Wall Street bosses to drop a couple of extra million, it’ll be worth it. That doesn’t stop him hating every second of it.

“So how much did you go for?” Bruce asks later that evening. Tony jumps, because Banner apparently enjoys sneaking up behind him with no warning.

“Uh. $4.8 million.” He says, and wow yeah, that’s kind of embarrassing. “It’s a weekend with Tony Stark now, apparently, although no-one thought to inform me of this. I might fire Pepper.”

“You wouldn’t survive three days without Pepper.” Bruce says flatly. He’s right, but Tony scowls at him anyway. “Well, I think it’s very generous of you, Tony. Who won?”

“I don’t know. Some rich old fart wanting advice about his stock portfolio, I imagine.”

“Well, I hope Pepper told them that sex isn’t included.” He adds casually.

Tony smirks. All of Bruce’s attempts to provoke a reaction are so obvious, it’s hardly any effort to rise above them. “This booty is extra.” He says seriously, and mentally punches the air when Bruce looks surprised. Point scored. “What?”

“Extra? Not out of the question entirely, but extra?”

“I thought you were meant to be Mr. Saves Sick Orphans and Dying Old Ladies. You’re telling me you wouldn’t suck a dick for charity?” He’s like, 80% joking, but he wants to see Bruce’s reaction. This is too much fun.

He takes a step closer to Tony, taps a finger against the concealed arc reactor and leans in to whisper in his ear. “Who’s to say I haven’t already?”

Tony’s mouth falls open, and Bruce acts totally innocent. “What? I… _What?_ You can’t just walk away after—Banner!” But Bruce continues walking towards the bar where Steve and Thor are enjoying a drink, and doesn’t even look over his shoulder. Points lost. So many points lost.

This man was going to be the death of him.


	2. The Pay Off

**Notes for the Chapter:**

> Aaaand part two. Thanks for sticking with me! Enjoy!

“Thank God you’re back.” Bruce says the second Tony steps into the lab. It has been the _longest_ weekend of his life. The guy that had actually paid $4.8 million for two days of his life was cripplingly boring and yes, did mainly want investment advice. He is so glad to be back home. “Take your shirt off now.”

“Good to see you too, Bruce.” He says, and dumps his bag on the floor. Bruce just stares at him. “You’re serious?”

“Take your damn shirt off, Tony.”

His fingers scrabble to yank the hem of his favourite AC/DC shirt over his head, wondering (and hoping) if this is going to go the way he wanted it to go. He’s only just pulled it free when Bruce’s fingers are on the arc reactor. “Jesus.” He hisses as Bruce’s rough fingers catch the rim of the metal disk. He sets about going to dislodge it from the casing, and Tony freezes. “Bruce, what are you— Stop it!”

Bruce, to his credit, steps away immediately, his face a mixture of concern and confusion. “Did I hurt you?” He asks, looking horrified.

Tony shakes his head and tries not to think about the last person who removed the reactor against his will. “N-Not really, I just…”

He seems to realise though. “Oh. _Oh._ God, Tony, I’m so sorry. I wasn’t thinking.”

Tony smiles weakly, and unclips the reactor from its base. He lifts it out gingerly and give it to Bruce, ignoring the pounding of his heart and the shaking of his hands.

“I had an idea while you were away.” He explains, looking apologetic as he cradles the glowing metal carefully. “It should cut the power usage by at least 21% from the initial consumption and—Are you sure you’re okay?”

“I’m fine. Go on.” He says, trying not to let his voice give him away. He feels vulnerable and uneasy, and he hates it. He hates feeling broken so much that he’d rather hide it from Bruce than accept that this is too much for today. “21%?”

Bruce isn’t stupid. He picks the wire up gently and reattaches the reactor before securing it back into place. “Improvements can wait. I’m really sorry, Tony.”

“Don’t sweat it.” He says, running a finger over the metal to reassure himself that it’s there, it’s working, he’s okay. “You’ve really got into this, haven’t you?”

Bruce looks away, embarrassed. “I get kind of obsessed when I’m working on new projects. It’s a good distraction, from…” He trails off, but Tony can fill in the rest of the sentence. “And it’s amazing. The arc reactor, it’s amazing. I mean, I’m no engineer but it’s like nothing I’ve ever seen before.”

“You know more about engineering than a lot of engineers I know.” Tony jokes, except it’s not a joke. Bruce really is remarkable. “And thanks. It’s nice to have someone appreciate my genius who actually understands how impressive it is.”

Bruce snorts. “God, you’re so arrogant.”

“And don’t I know it. Come on, why don’t you talk me through these improvements you’ve thought up? Then we can start them tomorrow.”

Bruce launches animatedly into a whole host of alterations and design modifications, and Tony listens intently. He’s not usually much of a listener; people usually don’t have that much to say to him that’s worth listening to. Bruce is an exception, and every word, every thought that he has is insightful and useful and intelligent.

He starts to show Tony what he means by touching at the arc reactor, but it’s with careful, gentle movements so as to not startle him or make him anxious. He’s not sure Bruce appreciates how sensitive the skin is. It’s more of a dull throb than actual pain, but he’s never experienced it over such a long time period before. And, well, Tony Stark can handle a little pain.

Enjoys it, in fact.

Enjoys it perhaps a little too much.

He grabs Bruce’s wrist lightly, and he stops gesturing. “Sorry, did I—” He asks, but Tony stops him finishing with ‘hurt you’ by kissing him square on the lips. Bruce pauses momentarily to assess the situation before kissing back.

“I thought you’d been checking me out.” Tony says accusatorily when they separate. His lips are still a mere inch from Bruce’s, and the temptation is almost overwhelming. “But you’ve just been gawking at the arc reactor this whole time.”

Bruce blushes, caught in the act like a naughty school boy. “I can’t help it.” He confesses. “It’s so fucking beautiful, Tony.” His thumb swipes across the border between metal and flesh, sending a shiver up Tony’s spine. “God. God. _You’re_ beautiful.”

“And here was me thinking you weren’t interested.” He manages to get the words out before Bruce is kissing him again, firm and wanting and insistent. His hands don’t leave the pale glow on his chest, and Tony gasps into his mouth, the sensation and the kissing and the fact that _he is making out with Bruce Banner while not wearing a shirt_ is all too much.

“Thought you were joking.” Bruce admits, moving his lips to Tony’s neck. He tips his head to the side, exposing skin for Bruce to kiss and bite to his heart’s content. It feels so good, so damn good. With the whole Avengers thing, no-one’s done this for him in weeks. He doesn’t care if his entire neck is black and blue from hickeys tomorrow, doesn’t care about the teasing he’ll get from Romanoff and Barton and Rogers. He can only focus on the here, the now, the feeling of Banner’s teeth nipping along his collarbone.

“Fuck, Bruce…” He moans, clenching a fist in the man’s curls. He fucking loves this, he loves that he can take handfuls of hair and cling on for dear life. Bruce apparently likes it too, his teeth and lips becoming more insistent as he reaches the hollow of his neck.

Tony knows what his target is now. He should have really known all along, but he’s too far gone to even make a snarky comment. All he can manage is a broken plea, and Bruce sweeps his tongue flat and wet across the surface of the reactor.

“O-Oh, shit—” He whimpers, and Bruce sits up straight instantly, looking for signs of distress on his face. “Fuckity _fuck_ , Banner, I swear to God—do that again right now.” Bruce grins, pleased that Tony’s enjoying himself, pleased that he’s not in any other kind of pain than the feeling of a giant hard-on in _really_ skinny jeans, and obeys.

Tony lets out a string of inappropriate language, and uses his grip on Bruce’s hair to hold his mouth to his chest, to make him lick and kiss and bite the tender flesh until he screams. It doesn’t take long. Bruce is masterful with that mouth, sinful, and that’s just on his fucking chest. Another lick across its diameter has Tony bucking his hips for something, anything, to grind against. He would use his hands but doesn’t want Bruce to take it as a sign to stop.

Unlike his, Bruce’s hands are free to explore, but the first Tony knows of it is a sharp burst of pain radiating from his right nipple. Bruce chuckles against his skin, and tugs again, on the left side this time. It’s like it travels out to the sensation from the ring of scarred flesh, and the whole of his chest tingles. It’s so fucking intense, but he needs more. He’ll never get enough of this. “Please, Bruce.” He chokes out, clenching his fists tighter because he’s forgotten all words other than _please_ and _more_ and _Bruce_ and he doesn’t know how else to communicate how good this feels.

He can’t imagine it getting any better until Bruce clamps his mouth around his nipple and sucks. Tony’s pretty sure he’s not even on Earth anymore; he’s spaced out and entering a whole new fucking dimension like his life is a damn Kubrick movie. He feels his nipple teased between Bruce’s teeth, enough pressure to hurt in a faint aching but nothing more. His thumb never stops moving, stroking absently around the curve of the metal, overloading Tony’s body with sensation until he emits a constant stream of nonsense, a low babble flowing freely from his mouth.

“Oh God, kiss me.” He blurts, forcing himself to hold his head up.

He watches Bruce’s red swollen lips curve into a satisfied smirk, but he does as he’s asked. Bruce kisses his like his life depends on it, and Tony takes it. He takes Bruce’s tongue pushing past his lips, exploring his mouth with the kind of eagerness he hasn’t known in a long time. Bruce fucking loves this, Tony realises, and he wants it as bad as Tony himself does.

Tony practically falls off his chair when the door slams open.

“We were just—” Bruce says hastily, sliding back from where he’d practically settled straddling Tony’s lap. “Um.”

Pepper grins at Bruce’s guilty expression. “Banner, relax. Tony wasn’t lying when he said our relationship was unusual. I’ve been waiting for this for weeks now.”

Bruce glances down to the ground to hide his blushing. It’s a brave new world for Banner, after all. “Potts, if this isn’t exceedingly important, you’re fired. And we’re breaking up.”

“It’s pretty important.” She says, but doesn’t go any further with Bruce in the room. She looks between the two of them, from Bruce’s swollen lips to the sucking and bite marks splattered across Tony’s chest. “But I can come back in a while if you’re busy.”

He nods furiously, so hard he can hardly function and would probably sign anything put under his nose right now if it meant getting back to Bruce, but Banner stands up. He sheepishly tugs his shirt down in a futile attempt to hide his obvious erection. “I’ll see you tomorrow, Tony. I’m sure it’s imperative that you handle it now, whatever it is.” He says, looking over his shoulder with a slight smirk. It’s partially his want to not intrude, but mostly, it’s the biggest point scoring move of the game so far. Bruce walks off, leaving Tony half naked, marked up and dick-crushingly hard.

He hates him. He completely, entirely, one hundred percent _hates_ him, the evil son of a bitch.

He also might be a little bit in love.

*

Since he found out that Bruce has, of all things, an _arc reactor kink_ , life in the Stark labs has got so much more eventful, if by eventful you mean even more sarcastic than usual. Bruce might have walked away with about twenty thousand points in their battle by leaving him to jerk himself off, but Tony can now use that fun little fact to tease Bruce constantly. And he does. Not a single opportunity is missed to throw in a quip, and Bruce fucking blushes every time.

Tony doesn’t wear a shirt in the lab any more. He’s pretty sure Pepper is pissed about him ‘flaunting safety protocol’, and Bruce still wears an actual lab coat because he’s a massive nerd, but he figures the occasional burn is worth the enjoyment of Banner trying not to stare too much.

They both end every session in the lab at least half hard.

Bruce can’t stop himself from touching all the time. Tony makes excuses for why he can’t take the reactor out unless they are actually working on it, and Bruce doesn’t question it. In reality, they ignore a lot of stuff that should probably be mentioned and act like this is totally normal. Half nude science. Tangible sexual tension.

It’s normal.

“Tony?”

Tony panics. Tony panics pretty much any time Bruce asks him anything because he doesn’t _get_ what’s going on here. It’s never been complicated like this before. He’s never been scared to make a move before, and he feels like anything he does is going to fuck up the tenuous balance they have struck. “Uh. Yeah?”

“Do you mind if I take it out?” He says with impressive calm. He won’t meet his eyes, though. “If we work quickly, we should be able to upgrade it and put it back in within the hour.”

“Bruce, you know I’m not that bothered how long it’s out. Within reason.” Tony has been fucking about on another project while Bruce finalises today’s upgrades, and his fingers are slippery with oil. Completely accidentally. Not planned at all. “You’re going to have to remove it, though. There’s no way I’m going to be able to grip it well enough to get it out.” And if everything he says sounds like a terrible innuendo, that’s just a happy coincidence.

Tony holds still as Bruce expertly unclips the reactor from its casing. He should be unnerved that someone else can do it so easily, but he trusts Bruce with his life. Literally. Like he’s literally holding Tony’s continued existence in his hands. He sets it carefully down on the work bench, makes sure it’s not going anywhere. “You okay, Tony?”

“No worse than usual.” He says honestly, and they set to work.

Bruce’s promise was right; fifty five minutes later, Bruce’s warm hands click cold metal back into place. “What are the readings, J?” He asks, and the AI mulls it over for a second. “23% improvement on original model.”

“Not bad. I still think we can make it a round 25% saving, though.” Bruce says, wiping his hands on his lab coat. It leaves little streaks of grease in his wake. His eyes linger on the glowing metal before he looks away in embarrassment. “Sorry. Shit, sorry.”

“Don’t apologise.” Tony purrs, putting his hand on Bruce’s chest for a change. He can feel his heart beating wildly under his fingers. There was a time that this would concern him, but he knows now it’s just the same adrenaline that’s coursing through his veins, not the Other Guy coming to play. “I like it.”

Bruce smiles weakly.

“You want to call it a day up here?” He suggests, thinking that this might be better taken downstairs.

“What? Oh. Yeah, sure. I guess I’ll see you later.”

“Don’t be stupid, Banner. I meant lose the whole terrible laboratory porn setting and take this to my bedroom.”

Bruce’s mouth falls open, and he steps back so Tony’s hand falls away. “I… But… But isn’t Pepper…”

“She’s on a business trip. And she likes you. And she keeps asking me when we’re going to fuck so you really need to stop worrying about her.”

Bruce pauses for a second to collect his thoughts. “Right. Okay. Yes. Yeah. Your room. … Okay.”

Tony smirks, takes three steps forward so he’s right in Bruce’s space, and kisses him. “God, sometimes you really need to talk less.” He opens his mouth like he’s going to protest, but then his eyes flick down, and he closes it again. “Or, I mean… If you’d prefer laboratory sex, we can fuck up here. I really don’t mind.”

“Bedroom is good.” He manages, and Tony beams. The elevator seems to take the most excruciatingly long time to get to his floor, and for once in his life his head has been wiped clean of topics for small talk. Not that anything would really be appropriate in this situation. What are you meant to say to someone while you’re on your way to have sex with them?

They eventually make it, and burst through the doors in a tangle of arms grabbing anything they can reach. Tony goes to flick the light switch, but Bruce stops him. “N-No. Leave them off.”

Tony is surprised; he always imagined Bruce was a low level mood lighting kind of guy, but then he realised. The reactor fills the room with an eerie glow, casting long shadows, and Bruce’s pupils are blown so wide that Tony can hardly see the ring of deep chocolate brown iris. Fucking hell. He scrabbles in his drawer for the lube stash he knows is in there. “You know, this thing was a more effective night light before you started making it all efficient.” He jokes, desperately feeling around in the near darkness. “Got it!” He throws it at Bruce and accidentally hits him in the shoulder. “You’re clean, right?”

“Wait, you want me to… to fuck you?” He says in surprise.

Tony smirks. He knows Bruce probably can’t see it, but whatever. “Yep. Got a problem with that, big guy?”

Bruce pauses for a second or two before responding. “Uh, no. I mean… No. I just presumed that you’d… Um.”

“Why do people always sound so god damn shocked that I like to bottom?” He wonders aloud, because it’s not the first time someone has made that assumption. He’s not exactly the manliest of guys—not that he finds that stereotype particularly accurate—but _everyone_ presumes he’s the toppiest top to ever top.

“Because you’re _Tony Stark_.” Bruce says helplessly, which isn’t really an answer but whatever.

“And Tony Stark likes it in the ass.” He says crudely. “Especially when the other guy is fucking hung.”

“How would you know?” Bruce retorts, his voice even. “You’ve never seen me naked; you have no reference for how big my dick is.”

Tony snorts. “Okay Bruce. Tell me right now that you don’t have a massive cock. Look me in the eye and sincerely tell me that you do not have a dick the size of the Empire State Building.”

“But like, what counts as a massive cock?” He argues, and fucking hell, only Bruce Banner could turn this into a bedroom debate on the statistical variance of penis length. “Are we measuring against the global average, or the North American average?”

“So you have a giant penis.” Tony grins. He has suspected as much, just one of those feelings. He’s already a hot genius; of course he also has a giant dick. Because the universe is unfair.

Bruce doesn’t answer for a moment, but silently begins unbuttoning his shirt. He folds it carefully and places it on a chair in the corner. Tony wants to say something but he’s struggling to put words together, because god damn, Bruce Banner looks good without a shirt.

He’s seen him shirtless before, but he didn’t count it. The Hulk isn’t great at looking after clothes, so everyone got a bit of an eyeful of a sweat soaked and shaking Bruce after the battle, but it wasn’t exactly an appropriate situation to be checking him out. Tony moves closer, part of him wanting to touch and the rest of him mainly wanting the only source of light left in the room to give him a better view.

Bruce meets his eyes; Tony is half expecting a nervous, blushing virgin approach but he is confident and sure of himself. Possibly more than Tony is himself. “And yes, in answer to your question. I am clean.”

“Cool. Can I…” Tony asks, gesturing at Bruce’s awful ugly slacks that look like they could actually fit the Other Guy in them without stretching an inch. Bruce nods, his breath catching slightly as Tony’s fingers brush against his stomach. He makes short work of the button and shoves them down Bruce’s legs, allowing him to step obediently out of them. Bruce is hard, tenting his boxers noticeably, and yeah he’s _definitely_ hung. His fingers dip under the waistband, and he looks up at Bruce to make sure he’s okay.

“Tony, I swear to God. Take them off.”

He does.

“Shit.” Bruce laughs. Tony can’t stop staring. “No, but… _Shit._ ” Like, he’s a massive size queen and he’s seen some impressive penises in his life but that thing is fucking _huge_.

“Sure you still want me to fuck you? No hard feelings if you don’t think you can handle me.” Bruce taunts, and Tony’s mouth is dry.

“Fuck. No. I need you to fuck me. I need that thing in me. Like, now.”

Bruce closes the gap between them, his dick pressing into Tony’s thigh, and kisses him hard. His fingers wrap in Tony’s hair, holding their lips together as he fucks his tongue into Tony’s mouth. “If you think you can take it.” He whispers into Tony’s ear as they break apart, then bites his earlobe with enough force to make him gasp.

Well, they do say it’s always the quiet ones.

“Please.” He croaks, and shoves his jeans to his ankles. Bruce laughs quietly as he does the honours and pushes Tony’s briefs down too.

He strokes him roughly, just one stroke before he lets go. “You know, you’re not doing too badly yourself, Stark.”  Tony bites down on his lip so he doesn’t embarrass himself by moaning or even worse, begging. How the hell does Banner have so much control when he himself is about to lose it like a twelve year old? “Bed.” Bruce instructs, but his voice cracks slightly. So maybe he’s not as put together as he would have Tony believe.

Tony collapses on to the bed, his cock curving up to his stomach, and Bruce settles between his legs. “Lube?” He asks, and Tony passes it from where it had landed next to the pillow. There’s the unmistakeable sound of the cap being snapped open, Bruce squeezing it onto his hand. “Ready?”

Tony hums. He’s more than ready; he needs it. No-one’s fucked him in a while, and he longs to feel full, to come so hard he can’t breathe, but it’s not just that. It’s _Bruce_. He really wants this from Bruce specifically. He’s totally infatuated.

The first finger slides in easily, probably over lubricated if he knows Banner at all. Bruce fucks it into him slowly, and Tony appreciates the effort, he does, but he’s way too damn turned on for all this foreplay. “Bruce, come on—”

Bruce frowns. “I don’t want to hurt you, Tony.”

“I’m not asking you to impale me on your monster dick, Banner. I’m asking you to stop fucking about and put another finger in my ass.”

Bruce snorts, but does as he’s asked. The extra finger adds a little more of a burn, a good pain that makes Tony’s breath hitch. He doesn’t bother with slow and steady any more, fucking his two fingers in roughly as Tony squirms underneath him.

“God, you’re good at that.” He moans, hips bucking up involuntarily. He’s pleasantly surprised, to be honest. Like, he’s always suspected Banner plays for both teams but he didn’t know how much experience the guy actually had. He’s impressed. Bruce’s fingers expertly find his prostate, pressing gently and quickly before going back to their steady rhythm and _fuck¸_ that feels good. Tony grabs a fistful of Bruce’s hair and pulls him closer, kissing him like the god damn world depended on it as he continued to stretch Tony open.

Bruce obliges, teeth catching his lips with just enough pressure to make him gasp. It’s like Bruce has his every reaction calculated. He knows exactly how much pressure is enough pressure, what speed is just slow enough to tease but fast enough to reduce him to a quivering moaning wreck. He hasn’t been so wholly taken apart like this in as long as he can remember.

“How are you so good at sex?” He gasps as the kiss breaks. He’s so fucking hard; his cock is leaking profusely on to his stomach but Bruce won’t give him enough to come. He doesn’t want to come, not yet anyway. This is too special to end so quickly.

“Practice.” He says simply. “I’m sure it’s the same for you. Not much recently of course, but… Well, I had the benefit of actually being an adult when I went to university.”

Tony scoffs. “Didn’t stop me.”

“I don’t think I want to know what you got up to as a sixteen year old at MIT.” He chuckles, and presses in another finger. Tony swears loudly, profusely and creatively, too distracted to correct him—he was fifteen, thank you very much. Bruce bends down and Tony thinks he’s going for another kiss, but he presses his mouth to the arc reactor. The sensitive flesh sparks, feels _amazing_ under Bruce’s lips, that perfect balance of pain and otherworldly pleasure.

“You’re so beautiful.” Bruce murmurs, looking up at him through half lidded eyes.

“Speak for yourself.” Tony gasps as Bruce’s fingers skim lightly over his prostate. “You really have a thing for it, don’t you?”

“I have a thing for you.” Bruce acknowledges, kissing the metal rim again.

“No, but… But the arc reactor. You have a _thing_ for it.” He can’t get his head around Bruce’s fascination with the cold metal, the ugly scarring, the evidence of his weakness. It’s a blemish on an otherwise flawless form—if he may say so himself—but the fusion of man and machine, it’s… it’s not normal..

“I have a thing for you.” Bruce repeats. “It’s part of you. No, it’s more than part of you. It _is_ you. This is the embodiment of everything that makes you great, Tony.”

“Well, that’s bad news, I guess.”

“It’s a god damn work of art, Tony, it’s genius. The entire world is trying to recreate it and they can’t. It’s…”

“Proof that Tony Stark has a heart?”

Bruce stops momentarily and Tony thinks he’s ruined it. “I wouldn’t word it like that.” He says slowly, like he’s considering the implications of it. “Did someone say that to you?”

Tony huffs out a laugh. “Pepper, but we were all in a bad place. Can you continue fingering me please?”

“I was going to say perseverance, actually. It’s you, living, even after everything. It’s your vitality.” He obliges and fucks his fingers into Tony again, and Tony has no idea how Bruce is managing to formulate a coherent argument. “Fine, whatever, okay. Yes.” He admits, and Tony frowns in confusion. “Yes, I have a thing for your arc reactor.”

“Knew it.”

Bruce pulls his fingers out without warning and wipes the smug look from Tony’s face. “Bruce, what are you—” He stops speaking when he sees Bruce picking up the condom with the faint eerie light of the arc reactor. “Oh. _Oh._ ”

“You still okay?” He checks, because Bruce Banner is a god damn wonderfully considerate person. Tony nods hurriedly, wanting nothing more than Bruce inside him right now, and Bruce smiles. “You think you can take me?” Tony nods, panting, desperate. “You taken anything bigger?”

Tony considers that for a second, mentally weighing up a catalogue of previous partners. He might not remember their name, but he remembers the important stuff. “Toys.” He says eventually, glancing down at Bruce spreading lube on to his dick. “Pepper has an impressive strap on collection.”

“But not another guy?” Tony shakes his head. “I’m honoured, Stark.”

He settles himself between Tony’s legs, getting into the ideal position to press into his hole when Tony has an idea. “Can I ride you?” He asks, sitting up a little straighter. “It’s not… It’s definitely not a deal breaker but I thought it could be… fun. For you.” Bruce looks perplexed. It’s an adorable look on him, but Tony takes pity. He manoeuvres them around so he can more easily straddle Bruce’s upper thighs, their hard dicks clashing between stomachs, and Bruce puts the pieces together. The arc reactor illuminates the space between their bodies, and Banner can even manage to do his favourite and make out with it if he lifts Tony up and stretches a little.

Bruce does a _lot_ of yoga. Bruce can handle it.

“F-Fuck, yeah. Yeah, this is good. Good idea.” Bruce runs his hands from Tony’s hips up his torso, and he can feel every callous and scratch of rough skin against his sides. “Really… Really good idea.” He leans down to touch his lips to the reactor, teeth scraping softly against the scarring. Tony moans, grinding his hips down into Bruce’s lap, but he doesn’t seem to notice. He’s too far gone.

“Bruce—fuck, Bruce, please.” Tony gasps.

“Am I—”

“You’re not hurting me! Not in a… a bad way, anyway. Fuck, if you keep doing that, you’re going to miss your window to fuck me.” He explained, his words punctuated with cussing and hitches where Bruce has actually literally taken his breath away. _God._

“Huh?” Bruce says in adorable confusion. He manages to prise himself away from Tony’s chest to look him in the eye, but Tony just gestures down at his cock. “Oh. Right.” He grins a little sheepishly, and snatches up the lube. “You like that, then?”

Tony laughs. “Jesus, Bruce, you think?”

Bruce slicks up his dick and helps Tony move into the right position. “Ready?” He asks, one hand on his dick and the other on Tony’s hip as a guide.

“I was born ready.” Tony jokes, trying not to overthink the feeling of Bruce’s dick pressing against his hole. He hasn’t had this in so long, and he’s desperate for it. He can tell Bruce’s cautious side is about to burst in spectacularly. “Bruce, if you hurt me, if I’m even a little bit uncomfortable, I will tell you. Now fucking _fuck me_.”

He laughs, and oh god oh god Bruce Banner’s dick is inside him.

Bruce lets Tony set the pace, and he sinks down slowly, just an inch or so. His hands grip Bruce’s shoulders like a lifeline as he fucks himself lower on each thrust. Bruce is biting his lip so hard he looks like he could break the skin, his head thrown back, eyes fluttered closed. He’s in fucking _bliss._

“You know you can’t see the arc reactor if you close your eyes like that.” Tony teases, managing another half inch or so before moving back up. Bruce’s eyes snap open like Tony thought they probably would, and he smirks. “You’re so predictable.”

“Well, you’re so… _Shit._ ” He swears, the cuss escaping his lips as Tony drops down a little further.

“I’m so shit?” Tony says in mock outrage. “You’re the first person to think so, Banner. In fact, most people think I’m really quite wonderful. Especially in the sack.” He takes a little more, and he’s at the point where he can’t fucking quite believe he hasn’t bottomed out yet. His legs shake with the strain of fucking himself down slowly, his thighs burning with exertion.

“And you’re very humble, too.” Bruce grins, his hands guiding Tony down a little further. “C’mon, baby…” He murmurs, and Tony gasps sharply as his ass meets Bruce’s thighs. “God, you feel so good.”

Tony takes a second to adjust and to catch his breath before laughing quietly. “Jesus, Banner, that was a work-out. The things I do to accommodate your kinks.”

Bruce grins and ducks his head to lick lightly across the top edge of the reactor. “It’s much appreciated, Stark. Definitely appreciated.”

Tony raises himself a little and drops back down, enjoying the sensation of being full, of Bruce’s warm body underneath him. He moves faster now that he’s confident he can take it, fucking himself down as fast as he can manage. Bruce attempts to keep his rhythm, but it’s still messy and unco-ordinated and they’re both too damn turned on to give a fuck.

“Tony, g-god…” Bruce moans underneath him, his words coming out broken and breathy as the pace increases. He sneaks a hand around Tony’s neck, thick fingers pressing hard into his skin. There’s every chance that’s going to bruise, and Steve will probably freak out, but Tony just doesn’t. Fucking. Care. He wants to feel Bruce everywhere, every damn place it’s possible for them to be touching. “You’re so hot.”

He barely manages to get the words out, his lips otherwise occupied with decorating his chest with bites. He scrapes his teeth across the join between skin and metal, and Tony jolts so hard that his thighs give way underneath him and he drops back on to Bruce’ lap. “Fuck!” He yells, the feeling of suddenly being impaled on Bruce’s cock a different one to the slow fucking he’s been doing this far.

It’s a good different. Definitely a good different. Pre-come smears on his stomach, beading from the top of his cock and it hasn’t even been touched yet. He is a total mess, pretty sure that if Bruce lays a damn _finger_ on him, he’ll come instantly like a twelve year old discovering porn. He’s so close already. Tony can’t remember the last time he’s got this worked up this quickly.

Tony half expects Bruce to apologise for being rough but he doesn’t. He fucking _growls_ under his breath, tightens his fingers on Tony’s neck and hip, guiding him into fucking harder, deeper, until Tony can hold off no longer. “Bruce, shit—I’m gonna come if you keep doing that.”

Bruce huffs out a laugh but doesn’t relent, increasing the pressure under his fingers and maintaining that brutal pace, as if he’s challenging Tony to see how long he can hold off for. “So come then.”

Tears actually prick at Tony’s eyes as he does exactly that, coming with impressive force all over his stomach. Bruce keeps fucking into him, slowing down and becoming more gentle with each thrust, the harsh scratches and bites around the arc reactor being replaced with sweet, soft kisses.   Just as the post-orgasm feeling is becoming too much, too sensitive, Bruce stops and Tony collapses onto him. “Fuck.” He says quietly, his head resting on Bruce’s shoulder in exhaustion.

He can still feel him, hard as a rock under him, but Bruce doesn’t seem overly bothered right now, content to just snuggle with Tony in his come-down. He carefully rolls Tony off of him, manoeuvres him into lying down on the bed. “You didn’t come.” Tony says accusatorily.

“You came so quickly I didn’t really have a chance to.” Bruce teases, but it’s obvious how close he is. It’s only due to Bruce’ impressive self-control that he hasn’t spunked everywhere already.

“I wanna blow you.” Tony ignores the jab; it feels like this foreplay has been going on for weeks and it’s been far too long since he had sex with someone, so it was kind of to be expected. He tries to sit up, but Bruce pushes him down again. “What? Come on, Bruce. I promise my blow jobs are very skilled.”

“Don’t want you to blow me.” He says, and moves so _he’s_ straddling Tony. He can’t work out what Bruce is doing, what he wants, until he touches himself with one light stroke and gasps slightly. “I want—” The words are lost in another moan as he speeds up his hand, and Tony knows he isn’t going to last long.

“Do it.” Tony gasps, trying to focus on breathing evenly because _God_ if he were young enough he’d be hard again already. Fuck fuck fuck fuck fuck. A strangled noise escaped Bruce’s throat as he gave in, come splattering across Tony’s chest, across the arc reactor, mixing with Tony’s come already there. “Oh god.”

Bruce chuckles and drags his finger across Tony’s chest, over the arc reactor, through the cooling mess coating it. He raises it to Tony’s lips and he doesn’t hesitate before parting them, sucking the come from Bruce shamelessly. “You’re so damn pretty like that.” Bruce tells him, his voice soft and quiet like it’s more to himself than to Tony.

“Am I not pretty all the time?” Tony asks, and yeah whatever he’s fishing for compliments but it’s so nice being with Bruce like this. He’s so relaxed, they both are, despite the gross stickiness and the abundance of sweat. 

“You know you are, Stark.” He laughs and moves to lie next to Tony, wiping his fingers on the sheet. “That was… really good.” He says to the ceiling. Their arms touch on the bed and Tony figures _fuck it_ and finds Bruce’s hand, winding their fingers together in a move that is more intimate than Tony is used to.

“It was.” He agrees. “I really like you, Bruce.”

The confession hangs in the air for a moment, its unspoken gravity magnified in the silence, until Bruce squeezes his hand lightly. “I really like you, too.” He tips his head to kiss the side of Tony’s face, and it’s sweet and awkward in an innocent way—although there’s not much innocent about the come drying on Tony’s chest. “We should clean up.” Bruce suggests it reluctantly, but Tony knows he’s right. He might be all fucked out and blissfully happy now, but he will greatly regret not washing in the morning.

“Come on, then.”

*

“Jesus, Stark. What happened?” Clint is obviously the first to make a comment the following morning. Bruce’s fingers did indeed bruise, but Tony didn’t give a fuck. He’s always been pretty susceptible to bruising anyway. “Did Banner get so fed up of you stealing his ideas that he _actually_ tried to strangle you?”

“You know, I’m offended that you think I have so little self-control.” Bruce chips in, coming in right behind Tony. Clint’s eyes somehow go even wider as he takes in the implications of this, of Bruce wearing one of Tony’s old MIT t-shirts over sweats, of Tony’s very slightly stilted walk.

“Oh my god.”

“And the penny drops.” Tony says sarcastically, and turns the coffee machine on.

“No but… You two are…”

Bruce takes his coffee from Tony with a serene smile. “As of yet undetermined.”

“But definitely a hypothesis worth looking into?” Tony responds casually, drinking from his scalding coffee like it was tap water.

“Oh, I’d say so. Wouldn’t you?”

Barton looks from one to the other, and rolls his eyes. “Fucking nerds.”

**Notes for the Chapter:**

> Come hang out with me on tumblr [ @scibros](http://scibros.tumblr.com) or hit me up with prompts or headcanons or just yell about how gay these two are in my inbox I literally don't care. Thanks for reading! <3

**Author's Note:**

> Hey guys, thanks for reading! As a side note, the brief reference to sexual acts for charity comes from a headcanon that tbh should just be canon from the fic Professionalism by ifitwasribald which is one of my all time favourite Science Boyfriends fics and possibly the best written blowjob in the history of the English language that was a long sentence
> 
> You can find me on tumblr [ @scibros ](http://scibros.tumblr.com) and remmeber we're still taking rolling applications for our Tony/Bruce network [ here ](http://tonybrucenetwork.tumblr.com/post/128266763658/rules-must-be-following-scibros-and-tonysbruce) so be sure to check that out. Until next time, amigos.


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